Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 44
Filtrar
1.
Facts Views Vis Obgyn ; 16(1): 35-45, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38551473

RESUMEN

Background: The LAparoscopic Versus Abdominal hysterectomy (LAVA) randomised controlled trial comparing laparoscopic hysterectomy (LH) and abdominal hysterectomy (AH) closed prematurely on the grounds of futility. Here we identify the challenges faced and lessons learnt. Objectives: To explore the views and experiences of clinical/research staff in order to understand how these might act as barriers to trial participation and recruitment. Materials and Methods: Review of the trial progress and collation of the views and experiences of clinical/ research staff on all aspects of the trial. Data were collected from transcribed conversations, email, phone, or video conferencing interactions and analysed descriptively. Main outcome measures: Site set-up milestones, recruitment rates and reasons provided by clinical/research staff for site's declining to participate. Opinions, preferences and experiences of clinicians/researchers and challenges to participation and recruitment. Results: The mean time from initial site contact to opening was 253 days and 68 days to randomise their first participant. 265 patients were screened from 13 sites over 13 months, 154 were eligible, and 75 (59%) were randomised. Of the 53 not randomised, 23 (43%) women preferred LH whilst 6 (11%) preferred AH. The main reasons given for failure to recruit or activate set-up in the 21 sites open or in set-up, were lack of research/ clinical capacity imposed by the COVID-19 pandemic and lack of clinician equipoise. Conclusions: The main reasons for the LAVA trial failure were lack of equipoise amongst surgeons and the adverse impact of the COVID-19 pandemic on clinical/research services. What is new?: Surgeons' preference for laparoscopic hysterectomy is not shared by most patients. Many patients prefer an open hysterectomy to a laparoscopic one.

2.
Trials ; 21(1): 436, 2020 May 27.
Artículo en Inglés | MEDLINE | ID: mdl-32460885

RESUMEN

BACKGROUND: Parkinson's disease (PD) affects approximately 145,519 people in the UK. Speech impairments are common with a reported prevalence of 68%, which increase physical and mental demands during conversation, reliance on family and/or carers, and the likelihood of social withdrawal reducing quality of life. In the UK, two approaches to Speech and Language Therapy (SLT) intervention are commonly available: National Health Service (NHS) SLT or Lee Silverman Voice Treatment (LSVT LOUD®). NHS SLT is tailored to the individuals' needs per local practice typically consisting of six to eight weekly sessions; LSVT LOUD® comprises 16 sessions of individual treatment with home-based practice over 4 weeks. The evidence-base for their effectiveness is inconclusive. METHODS/DESIGN: PD COMM is a phase III, multicentre, three-arm, unblinded, randomised controlled trial. Five hundred and forty-six people with idiopathic PD, reporting speech or voice problems will be enrolled. We will exclude those with a diagnosis of dementia, laryngeal pathology or those who have received SLT for speech problems in the previous 2 years. Following informed consent and completion of baseline assessments, participants will be randomised in a 1:1:1 ratio to no-intervention control, NHS SLT or LSVT LOUD® via a central computer-generated programme, using a minimisation procedure with a random element, to ensure allocation concealment. Participants randomised to the intervention groups will start treatment within 4 (NHS SLT) or 7 (LSVT LOUD®) weeks of randomisation. PRIMARY OUTCOME: Voice Handicap Index (VHI) total score at 3 months. Secondary outcomes include: VHI subscales, Parkinson's Disease Questionnaire-39; Questionnaire on Acquired Speech Disorders; EuroQol-5D-5 L; ICECAP-O; resource utilisation; adverse events and carer quality of life. Mixed-methods process and health economic evaluations will take place alongside the trial. Assessments will be completed before randomisation and at 3, 6 and 12 months after randomisation. The trial started in December 2015 and will run for 77 months. Recruitment will take place in approximately 42 sites around the UK. DISCUSSION: The trial will test the hypothesis that SLT is effective for the treatment of speech or voice problems in people with PD compared to no SLT. It will further test whether NHS SLT or LSVT LOUD® provide greater benefit and determine the cost-effectiveness of both interventions. TRIAL REGISTRATION: International Standard Randomised Controlled Trials Number (ISRCTN) Registry, ID: 12421382. Registered on 18 April 2016.


Asunto(s)
Terapia del Lenguaje/métodos , Enfermedad de Parkinson/complicaciones , Logopedia/métodos , Trastornos de la Voz/rehabilitación , Voz , Ensayos Clínicos Fase III como Asunto , Análisis Costo-Beneficio , Humanos , Estudios Multicéntricos como Asunto , Calidad de Vida , Ensayos Clínicos Controlados Aleatorios como Asunto , Encuestas y Cuestionarios , Reino Unido , Trastornos de la Voz/etiología
3.
J Chem Phys ; 148(4): 040901, 2018 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-29390804

RESUMEN

The multipolar Hamiltonian of quantum electrodynamics is extensively employed in chemical and optical physics to treat rigorously the interaction of electromagnetic fields with matter. It is also widely used to evaluate intermolecular interactions. The multipolar version of the Hamiltonian is commonly obtained by carrying out a unitary transformation of the Coulomb gauge Hamiltonian that goes by the name of Power-Zienau-Woolley (PZW). Not only does the formulation provide excellent agreement with experiment, and versatility in its predictive ability, but also superior physical insight. Recently, the foundations and validity of the PZW Hamiltonian have been questioned, raising a concern over issues of gauge transformation and invariance, and whether observable quantities obtained from unitarily equivalent Hamiltonians are identical. Here, an in-depth analysis of theoretical foundations clarifies the issues and enables misconceptions to be identified. Claims of non-physicality are refuted: the PZW transformation and ensuing Hamiltonian are shown to rest on solid physical principles and secure theoretical ground.

4.
J Vet Intern Med ; 32(1): 72-85, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-29214723

RESUMEN

BACKGROUND: Changes in clinical variables associated with the administration of pimobendan to dogs with preclinical myxomatous mitral valve disease (MMVD) and cardiomegaly have not been described. OBJECTIVES: To investigate the effect of pimobendan on clinical variables and the relationship between a change in heart size and the time to congestive heart failure (CHF) or cardiac-related death (CRD) in dogs with MMVD and cardiomegaly. To determine whether pimobendan-treated dogs differ from dogs receiving placebo at onset of CHF. ANIMALS: Three hundred and fifty-four dogs with MMVD and cardiomegaly. MATERIALS AND METHODS: Prospective, blinded study with dogs randomized (ratio 1:1) to pimobendan (0.4-0.6 mg/kg/d) or placebo. Clinical, laboratory, and heart-size variables in both groups were measured and compared at different time points (day 35 and onset of CHF) and over the study duration. Relationships between short-term changes in echocardiographic variables and time to CHF or CRD were explored. RESULTS: At day 35, heart size had reduced in the pimobendan group: median change in (Δ) LVIDDN -0.06 (IQR: -0.15 to +0.02), P < 0.0001, and LA:Ao -0.08 (IQR: -0.23 to +0.03), P < 0.0001. Reduction in heart size was associated with increased time to CHF or CRD. Hazard ratio for a 0.1 increase in ΔLVIDDN was 1.26, P = 0.0003. Hazard ratio for a 0.1 increase in ΔLA:Ao was 1.14, P = 0.0002. At onset of CHF, groups were similar. CONCLUSIONS AND CLINICAL IMPORTANCE: Pimobendan treatment reduces heart size. Reduced heart size is associated with improved outcome. At the onset of CHF, dogs treated with pimobendan were indistinguishable from those receiving placebo.


Asunto(s)
Cardiotónicos/uso terapéutico , Prolapso de la Válvula Mitral/tratamiento farmacológico , Piridazinas/uso terapéutico , Animales , Cardiomegalia/tratamiento farmacológico , Cardiomegalia/veterinaria , Enfermedades de los Perros/tratamiento farmacológico , Perros , Ecocardiografía/veterinaria , Cardiopatías/mortalidad , Cardiopatías/veterinaria , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/veterinaria , Prolapso de la Válvula Mitral/diagnóstico por imagen , Prolapso de la Válvula Mitral/patología , Estudios Prospectivos , Calidad de Vida
5.
Public Health ; 146: 4-9, 2017 May.
Artículo en Inglés | MEDLINE | ID: mdl-28404473

RESUMEN

OBJECTIVES: Hospital Episode Statistics data are used for healthcare planning and hospital reimbursements. Reliability of these data is dependent on the accuracy of individual hospitals reporting Secondary Uses Service (SUS) which includes hospitalisation. The number and coding accuracy for Parkinson's disease hospital admissions at a tertiary centre in Birmingham was assessed. STUDY DESIGN: Retrospective, routine-data-based study. METHODS: A retrospective electronic database search for all Parkinson's disease patients admitted to the tertiary hospital over a 4-year period (2009-2013) was performed on the SUS database using International Classification of Disease codes, and on the local inpatient electronic prescription database, Prescription and Information Communications System, using medication prescriptions. Capture-recapture methods were used to estimate the number of patients and admissions missed by both databases. RESULTS: From the two databases, between July 2009 and June 2013, 1068 patients with Parkinson's disease accounted for 1999 admissions. During these admissions, the Parkinson's disease was coded as a primary or secondary diagnosis. Ninety-one percent of these admissions were recorded on the SUS database. Capture-recapture methods estimated that the number of Parkinson's disease patients admitted during this period was 1127 patients (95% confidence interval: 1107-1146). A supplementary search of both SUS and Prescription and Information Communications System was undertaken using the hospital numbers of these 1068 patients. This identified another 479 admissions. SUS database under-estimated Parkinson's disease admissions by 27% during the study period. CONCLUSION: The accuracy of disease coding is critical for healthcare policy planning and must be improved. If the under-reporting of Parkinson's disease admissions on the SUS database is repeated nationally, expenditure on Parkinson's disease admissions in England is under-estimated by approximately £61 million per year.


Asunto(s)
Codificación Clínica , Planificación en Salud , Hospitalización/estadística & datos numéricos , Enfermedad de Parkinson/terapia , Anciano , Anciano de 80 o más Años , Bases de Datos Factuales , Femenino , Humanos , Clasificación Internacional de Enfermedades , Masculino , Reproducibilidad de los Resultados , Estudios Retrospectivos , Reino Unido
6.
J Chem Phys ; 145(14): 147102, 2016 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-27782519

RESUMEN

The 'problem' identified in the paper [J. Chem.Phys. 144, 044109 (2016)] does not arise in a properly formulated non-relativistic Hamiltonian formalism for both classical and quantum electrodynamics.

7.
J Vet Intern Med ; 30(6): 1765-1779, 2016 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-27678080

RESUMEN

BACKGROUND: Pimobendan is effective in treatment of dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD). Its effect on dogs before the onset of CHF is unknown. HYPOTHESIS/OBJECTIVES: Administration of pimobendan (0.4-0.6 mg/kg/d in divided doses) to dogs with increased heart size secondary to preclinical MMVD, not receiving other cardiovascular medications, will delay the onset of signs of CHF, cardiac-related death, or euthanasia. ANIMALS: 360 client-owned dogs with MMVD with left atrial-to-aortic ratio ≥1.6, normalized left ventricular internal diameter in diastole ≥1.7, and vertebral heart sum >10.5. METHODS: Prospective, randomized, placebo-controlled, blinded, multicenter clinical trial. Primary outcome variable was time to a composite of the onset of CHF, cardiac-related death, or euthanasia. RESULTS: Median time to primary endpoint was 1228 days (95% CI: 856-NA) in the pimobendan group and 766 days (95% CI: 667-875) in the placebo group (P = .0038). Hazard ratio for the pimobendan group was 0.64 (95% CI: 0.47-0.87) compared with the placebo group. The benefit persisted after adjustment for other variables. Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (median survival time was 1059 days (95% CI: 952-NA) in the pimobendan group and 902 days (95% CI: 747-1061) in the placebo group) (P = .012). CONCLUSIONS AND CLINICAL IMPORTANCE: Administration of pimobendan to dogs with MMVD and echocardiographic and radiographic evidence of cardiomegaly results in prolongation of preclinical period and is safe and well tolerated. Prolongation of preclinical period by approximately 15 months represents substantial clinical benefit.


Asunto(s)
Cardiomegalia/veterinaria , Cardiotónicos/uso terapéutico , Enfermedades de los Perros/tratamiento farmacológico , Insuficiencia de la Válvula Mitral/veterinaria , Piridazinas/uso terapéutico , Animales , Cardiomegalia/tratamiento farmacológico , Cardiotónicos/efectos adversos , Perros , Femenino , Insuficiencia Cardíaca/tratamiento farmacológico , Insuficiencia Cardíaca/mortalidad , Insuficiencia Cardíaca/veterinaria , Masculino , Insuficiencia de la Válvula Mitral/tratamiento farmacológico , Insuficiencia de la Válvula Mitral/mortalidad , Piridazinas/efectos adversos
8.
J Biomed Nanotechnol ; 10(7): 1336-45, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-24804554

RESUMEN

An in-depth understanding of biochemical processes occurring within biological systems is key for early diagnosis of disease and identification of appropriate treatments. Nanobiophotonics offers huge potential benefits for intracellular diagnostics and therapeutics. Intracellular sensing using fluorescent nanoparticles is a potentially useful tool for real-time, in vivo monitoring of important cellular analytes. This work is focused on synthesis of optical chemical nanosensors for the quantitative analysis of pH inside living cells. The structure of the nanosensor comprises a biofriendly silica matrix with co-encapsulated Texas Red, acting as a reference dye, and pH-sensitive fluorescein isothiocyanate enabling ratiometric quantitative environmental detection. In order to obtain silica-based nanoparticles -70 nm in size, a modified sol-gel-based Stöber method was employed. The potential of these nanosensors for intracellular pH monitoring is demonstrated inside a live human embryonic kidney cell line whereby a significant change in fluorescence is observed when the cell pH is switched from acidic to basic. High loading efficiencies of nanoparticles into the cells is seen, with little effect on cell morphology even following extended nanoparticle exposure (up to 72 h). Nanoparticle incubation time and the fast response of the nanosensor (-2 s) make it a very powerful tool in monitoring the processes occurring within the cytosol.


Asunto(s)
Técnicas Biosensibles/métodos , Espacio Intracelular/metabolismo , Nanopartículas/química , Dióxido de Silicio/química , Calibración , Muerte Celular , Células HEK293 , Humanos , Concentración de Iones de Hidrógeno , Luz , Microscopía Fluorescente , Nanopartículas/ultraestructura , Dispersión de Radiación , Espectrometría de Fluorescencia , Factores de Tiempo , Receptor Toll-Like 4/metabolismo
10.
Analyst ; 138(16): 4512-8, 2013 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-23752224

RESUMEN

Platelets are central in maintaining normal haemostasis and are responsible for the cessation of blood loss following vascular injury. Platelet adhesion, leading to thrombus formation, involves rapid and distinct morphological changes culminating in cell aggregation. Rapid and highly specific platelet diagnostic tests are currently being developed to enable monitoring of drug response in patients with cardiovascular diseases. For a diagnostic device to be effective it needs to be rapid and simple, requiring minimal user interaction and providing results with minimal delay. This study describes the development of a rapid, label free platform for assay platelet function and demonstrates its use to monitor the influence of anti-thrombotic drugs. A rapid, single-step cell purification surface immobilises platelets from whole blood onto a protein array at specific locations used to define the assay site. Morphological changes and cell aggregation properties of activated platelets are exploited and combined within a label free, rapid, dye displacement chamber to determine cell morphology. Stimulation-dependent changes in cell morphology are described using both high resolution AFM imaging and a dye displacement platform.


Asunto(s)
Activación Plaquetaria , Análisis por Matrices de Proteínas/métodos , Humanos , Microscopía de Fuerza Atómica/métodos , Microscopía Fluorescente/métodos , Activación Plaquetaria/fisiología , Pruebas de Función Plaquetaria/métodos , Factores de Tiempo
11.
Nanomedicine ; 9(4): 540-9, 2013 May.
Artículo en Inglés | MEDLINE | ID: mdl-23117042

RESUMEN

Nanoparticles are increasingly used as diagnostic tools due to the ease with which their surface chemistry, optical and physical properties can be controlled. Molecules, drugs, enzymes and fluorophores can be protected within the particle core or conjugated externally conferring nanoparticle biocompatibility, target specificity or environmental sensitivity. This study details the development and characterisation of stable, bright, dye-doped silica nanoparticles which are surface functionalised with PAMAM dendrimers to enable efficient conjugation to platelet activation-specific antibodies. We present the physical and optical properties and demonstrate colloidal stability. We also provide the first evidence of how NPs can be employed to specifically label human platelets immobilised on a lab-on-a-chip platform. Using a single step protocol, we demonstrate highly specific platelet labelling with the distribution of antibody-conjugated NPs matching that expected for the platelet GPIIb/IIIa receptor. The work highlights the potential of functionalized fluorescent NPs as diagnostic tools for cardiovascular disease. FROM THE CLINICAL EDITOR: This study details the development and characterization of PAMAM dendrimer functionalized, stable, and bright dye-doped silica nanoparticles that enable efficient conjugation to platelet activation-specific antibodies. These fluorescent NPs may specifically label human platelets that can be used as diagnostic tools for cardiovascular disease.


Asunto(s)
Plaquetas , Fluorescencia , Nanopartículas , Coloides , Dendrímeros
12.
J Chem Phys ; 137(22): 22A544, 2012 Dec 14.
Artículo en Inglés | MEDLINE | ID: mdl-23249081

RESUMEN

Transition state theory was introduced in 1930s to account for chemical reactions. Central to this theory is the idea of a potential energy surface (PES). It was assumed that such a surface could be constructed using eigensolutions of the Schrödinger equation for the molecular (Coulomb) Hamiltonian but at that time such calculations were not possible. Nowadays quantum mechanical ab initio electronic structure calculations are routine and from their results PESs can be constructed which are believed to approximate those assumed derivable from the eigensolutions. It is argued here that this belief is unfounded. It is suggested that the potential energy surface construction is more appropriately regarded as a legitimate and effective modification of quantum mechanics for chemical purposes.

13.
J Small Anim Pract ; 49(11): 587-92, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19006490

RESUMEN

OBJECTIVES: To investigate the prognostic and diagnostic value of heart rate variability (HRV) using the vasovagal tonus index (VVTI) in dogs suffering from idiopathic dilated cardiomyopathy (DCM). METHODS: Electrocardiographic (ECG) recordings of 369 patients presented to a referral centre between 1993 and 2006 were reviewed. RESULTS: VVTI values were calculated from 132 dogs. Lower VVTI values were found in patients in International Small Animal Cardiac Health Council (ISACHC) heart failure (HF) class 2 and 3 compared with class 1. VVTI was found to be positively correlated with survival time (ST) in class 2 and 3 patients. When a cut-off value of 7.59 for VVTI was used, the test could differentiate patients in ISACHC HF class 1 versus 2 and 3 with a sensitivity of 89 per cent and a specificity of 62.5 per cent. The ST for patients with VVTI values less than 7.59 was significantly lower. CLINICAL SIGNIFICANCE: The VVTI is a useful index, obtained from a standard ECG recording that estimates HRV in dogs and does not require any specific equipment for its calculation. It can be useful as a diagnostic tool to assess the severity of HF and is a useful prognostic tool in dogs with DCM.


Asunto(s)
Cardiomiopatía Dilatada/veterinaria , Enfermedades de los Perros/diagnóstico , Enfermedades de los Perros/fisiopatología , Frecuencia Cardíaca , Índice de Severidad de la Enfermedad , Animales , Cardiomiopatía Dilatada/diagnóstico , Cardiomiopatía Dilatada/mortalidad , Cardiomiopatía Dilatada/fisiopatología , Enfermedades de los Perros/mortalidad , Perros , Electrocardiografía/veterinaria , Femenino , Modelos Lineales , Masculino , Valor Predictivo de las Pruebas , Pronóstico , Curva ROC , Estudios Retrospectivos , Análisis de Supervivencia
14.
Int J Clin Pract ; 62(1): 148-51, 2008 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-18021208

RESUMEN

INTRODUCTION: There is a large population of elderly medical inpatients with co-existent medical and mental health disorders who pose a significant management challenge for medical, nursing and allied staff. Our hospital has a joint elderly medicine-psychiatry unit to cater for this patient group; this article reviews how this unit was set up and presents a representative sample of inpatients. RESULTS: The mean age was 81 years with a female preponderance. The mean length of stay was 44 days. The commonest medical conditions were cerebrovascular disease, urinary tract infections, chest infections and falls. The commonest mental health diagnoses were cognitive impairment, delirium and depression. The mortality rate was 21%; of the remainder, 55% were discharged to long-term care, 40% returned home and 5% were transferred to the local psychiatric hospital. DISCUSSION: This cohort of elderly patients has complex medical, nursing and therapy needs in addition to complex discharge planning needs. Our unit has a shared care approach, with joint responsibility shared by a consultant in Medicine for the Elderly and a Consultant in Old Age Psychiatry. This, in combination with a multidisciplinary team approach, provides an effective means of delivering care to this patient group. CONCLUSION: A joint elderly medicine-old age psychiatry ward provides a high standard of care for elderly patients with co-existent physical and mental health needs. We hope that the information presented in this article will be of use to those hoping to set up a similar unit in their own hospitals.


Asunto(s)
Prestación Integrada de Atención de Salud/organización & administración , Servicios de Salud para Ancianos/organización & administración , Grupo de Atención al Paciente/organización & administración , Servicio de Psiquiatría en Hospital/organización & administración , Anciano , Anciano de 80 o más Años , Inglaterra , Femenino , Humanos , Masculino , Trastornos Mentales/terapia , Habitaciones de Pacientes/organización & administración
15.
J Small Anim Pract ; 48(8): 455-7, 2007 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-17425699

RESUMEN

A 10-year-old male cairn terrier cross was presented with a history of myxomatous mitral valve disease diagnosed six months previously and with a four-week history of intermittent collapse. On 24 hour electrocardiograph (Holter) analysis, periods of no discernable electrical cardiac activity, which coincided with three collapsing episodes, were identified. Unfortunately, on re-presentation for removal of the Holter monitor, the dog collapsed and died. A post-mortem examination was conducted, and histology of the right and left atrium showed evidence of myocarditis. This is the first reported case, to our knowledge, of collapse because of electrical asystole in a dog with atrial myocarditis.


Asunto(s)
Enfermedades de los Perros/diagnóstico , Atrios Cardíacos/patología , Insuficiencia de la Válvula Mitral/veterinaria , Miocarditis/veterinaria , Animales , Muerte Súbita/veterinaria , Diagnóstico Diferencial , Enfermedades de los Perros/patología , Perros , Electrocardiografía Ambulatoria/veterinaria , Masculino , Insuficiencia de la Válvula Mitral/complicaciones , Insuficiencia de la Válvula Mitral/diagnóstico , Miocarditis/complicaciones , Miocarditis/diagnóstico
16.
Phys Chem Chem Phys ; 7(21): 3664-76, 2005 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-16358012

RESUMEN

A number of recent papers have considered ways in which molecular structure may be calculated when both the electrons and the nuclei are treated from the outset as quantum particles. This is in contrast to the conventional approach in which the nuclei initially have their positions fixed and so merely provide a potential for electronic motion. The usual approach is generally assumed to be justified by the 1927 work of Born and Oppenheimer. In this paper we discuss what precisely might be anticipated in the way of molecular structure from a mathematical consideration of the spectral properties of the full Coulomb Hamiltonian, to what extent the very idea of molecular structure might be dependent upon treating the nuclei simply as providing a potential and the extent to which the work of Born and Oppenheimer can be used to support this position.


Asunto(s)
Algoritmos , Modelos Químicos , Modelos Moleculares , Estructura Molecular , Teoría Cuántica , Electricidad Estática , Simulación por Computador , Interacciones de Partículas Elementales , Partículas Elementales
17.
Water Sci Technol ; 47(7-8): 1-9, 2003.
Artículo en Inglés | MEDLINE | ID: mdl-12793655

RESUMEN

The Brazil Development Study investigates the feasibility of alternative approaches to providing sustainable water services to a 226 ha mixed residential and industrial greenfield development within the city of Brisbane, Australia. The alternatives include techniques such a the use of rainwater tanks, water use efficiency, a local wastewater treatment plant for recycling of reclaimed water and composting toilets amongst others. This paper evaluates a series of urban development scenarios against the objectives of the study. The insights gained into the drivers for cost and environmental impact for this particular site are discussed as well as a number of issues of concern and challenges to Council and the community.


Asunto(s)
Conservación de los Recursos Naturales , Eliminación de Residuos Líquidos , Abastecimiento de Agua , Ciudades , Evaluación de Programas y Proyectos de Salud , Queensland
18.
Biochemistry ; 40(42): 12727-37, 2001 Oct 23.
Artículo en Inglés | MEDLINE | ID: mdl-11601998

RESUMEN

The fluorescence emission intensity from a conserved tryptophan residue (W501) located in the relay loop (F466 to L516) of the Dicytostelium discoideum myosin II motor domain is sensitive to ATP binding and hydrolysis. The initial binding process is accompanied by a small quench in fluorescence, and this is followed by a large enhancement that appears coincident with the hydrolysis step. Using temperature and pressure jump methods, we show that the enhancement process is kinetically distinct from but coupled to the hydrolysis step. The fluorescence enhancement corresponds to the open-closed transition (k(obs) approximately 1000 s(-1) at 20 degrees C). From the overall steady-state fluorescence signal and the presence or absence of a relaxation transient, we conclude that the ADP state is largely in the open state, while the ADP.AlF(4) state is largely closed. At 20 degrees C the open-closed equilibria for the AMP.PNP and ADP.BeF(x) complexes are close to unity and are readily perturbed by temperature and pressure. In the case of ATP, the equilibrium of this step slightly favors the open state, but coupling to the subsequent hydrolysis step gives rise to a predominantly closed state in the steady state. Pressure jump during steady-state ATP turnover reveals the distinct transients for the rapid open-closed transition and the slower hydrolysis step.


Asunto(s)
Adenosina Trifosfato/metabolismo , Dictyostelium/química , Dictyostelium/genética , Miosina Tipo II/química , Miosina Tipo II/genética , Triptófano/análogos & derivados , Triptófano/química , Triptófano/genética , Animales , Frío , Calor , Hidrólisis , Cinética , Proteínas Motoras Moleculares/química , Proteínas Motoras Moleculares/genética , Mutagénesis Sitio-Dirigida , Presión , Conformación Proteica , Estructura Terciaria de Proteína/genética , Espectrometría de Fluorescencia/instrumentación , Espectrometría de Fluorescencia/métodos , Triptófano/metabolismo
19.
J Biol Chem ; 276(22): 19483-90, 2001 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-11278775

RESUMEN

Steady-state and time-resolved fluorescence measurements were performed on a Dictyostelium discoideum myosin II motor domain construct retaining a single tryptophan residue at position 501, located on the relay loop. Other tryptophan residues were mutated to phenylalanine. The Trp-501 residue showed a large enhancement in fluorescence in the presence of ATP and a small quench in the presence of ADP as a result of perturbing both the ground and excited state processes. Fluorescence lifetime and quantum yield measurements indicated that at least three microstates of Trp-501 were present in all nucleotide states examined, and these could not be assigned to a particular gross conformation of the motor domain. Enhancement in emission intensity was associated with a reduction of the contribution from a statically quenched component and an increase in a component with a 5-ns lifetime, with little change in the contribution from a 1-ns lifetime component. Anisotropy measurements indicated that the Trp-501 side chain was relatively immobile in all nucleotide states, and the fluorescence was effectively depolarized by rotation of the whole motor domain with a correlation time on 50-70 ns. Overall these data suggest that the backbone of the relay loop remains structured throughout the myosin ATPase cycle but that the Trp-501 side chain experiences a different weighting in local environments provided by surrounding residues as the adjacent converter domain rolls around the relay loop.


Asunto(s)
Dictyostelium/química , Dictyostelium/fisiología , Triptófano/química , Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Anisotropía , Clonación Molecular , Cinética , Modelos Químicos , Miosinas/metabolismo , Fenilalanina/química , Estructura Terciaria de Proteína , Espectrometría de Fluorescencia , Espectrofotometría , Factores de Tiempo
20.
Biochemistry ; 39(51): 16135-46, 2000 Dec 26.
Artículo en Inglés | MEDLINE | ID: mdl-11123942

RESUMEN

When myosin interacts with ATP there is a characteristic enhancement in tryptophan fluorescence which has been widely exploited in kinetic studies. Using Dictyostelium motor domain mutants, we show that W501, located at the end of the relay helix close to the converter region, responds to two independent conformational events on nucleotide binding. First, a rapid isomerization gives a small fluorescence quench and then a slower reversible step which controls the hydrolysis rate (and corresponds to the open-closed transition identified by crystallography) gives a large enhancement. A mutant lacking W501 shows no ATP-induced enhancement in the fluorescence, yet quenched-flow measurements demonstrate that ATP is rapidly hydrolyzed to give a products complex as in the wild-type. The nucleotide-free, open and closed states of a single tryptophan-containing construct, W501+, show distinct fluorescence spectra and susceptibilities to acrylamide quenching which indicate that W501 becomes internalized in the closed state. The open-closed transition does not require hydrolysis per se and can be induced by a nonhydrolyzable analogue. At 20 degrees C, the equilibrium may favor the open state, but with ATP as substrate, the subsequent hydrolysis step pulls the equilibrium toward the closed state such that a tryptophan mutant containing only W501 yields an overall 80% enhancement. These studies allow solution-based assays to be rationalized with the crystal structures of the myosin motor domain and show that three different states can be distinguished at the interface of the relay and converter regions.


Asunto(s)
Adenosina Trifosfato/análogos & derivados , Adenosina Trifosfato/química , Proteínas Motoras Moleculares/química , Mutagénesis Sitio-Dirigida , Miosinas/química , Triptófano/genética , Adenosina Difosfato/química , Adenilil Imidodifosfato/química , Compuestos de Aluminio/química , Animales , Sitios de Unión , Cristalografía por Rayos X , Dictyostelium , Fluoruros/química , Hidrólisis , Cinética , Proteínas Motoras Moleculares/genética , Miosinas/genética , Conformación Proteica , Estructura Terciaria de Proteína/genética , Espectrometría de Fluorescencia , Triptófano/química
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA